Microtubule based motility is critical to the life and growth of eukaryotic cells. Cytoplasmic dynein is a multisubunit protein complex and is the principal motor for minus end directed transport along microtubules. Its ability to transport a wide array of cargo is due in part to the diversity of the light and intermediate chain subunits at its base. This proposal focuses on the interactions of light chains and intermediate chains that form a subcomplex at the dynein base. The first aim is to characterize the changes in conformation that accompany dissociation of dimeric light chain LC8. This will be done by comparing hydrogen deuterium exchange mass spectrometry (HXMS) of dimeric LC8 to the monomeric mutant H55K. The second aim is to characterize the interactions between LC8 and intermediate chain IC74 also using HXMS and on line light scattering. The purpose here is to map the segments that get protected upon binding, and the increase in ordered structure that accompany binding. The third aim is to characterize the interactions of LC8, IC74 and another light chain Tctex-1 using HXMS and online light scattering. The purpose here is to test whether binding of Tctex-1 causes the flexible intermediate chain to become more ordered. [unreadable] [unreadable]